Adjustable stroke hydraulic motor



Oct. 21, 1952 QB. LIVERS ADJUSTABLE STROKE HYDRAULIC MOTOR Filed May 16, 1949 R Y m N S R m m m m w m w\ Q N\ QN wv My QQ wwm Q Saw m MN mu SQN NM N associated valves of! their seats. "The "plug 46 is normally maintained in a leftmost position, as shown in Fig. l, by a helical compression spring .49 which is partially positioned in a, passage 50 within the plug 46. This ,passage 50, together with a smaller continuing passage 51 intercommunicates the opposite ends .of the plug 46 :so

that fluid is not compressed or expanded between the right end of the passage 38 and the plug. The communication between the passage 35 and the passage 39 is efiected through the an nular recess inthe plug 46 which defines the conical surface 46a, and this space is segregated from communication with the left end of the floating piston by sealingrings -2 and 53 respectively. i

*The :cam [plug 46 can be actuated to the right, tolift the valve balls .28 and 4.1, :by rotationof a cross shaft 5?! in the cylinder head I I, which cross shaft is shown as .having an actuating arm 58 ,on its outer .end. Suitable sealing means is provided to prevent leakage of fluid around the shaft 51 to the exterior. The shaft is provided with a :flat. surface 51a juxtaposed to the left end of thecam plug 46, so that rocking of the-shaft in either direction from its normal position shifts the actuator plug 46 to the right.

The 'operationof the-device is as follows:

As shown in Fig. 1, the floating piston 20 and working piston .l 9 are in contact with each other, and the floating piston is in the extremeleft end of the cylinder .10. If pressure fluid is admitted tothe port l6 and exhausted from the port 18, both vpistons will .be moved as a unit from the leftend of the cylinder to the right, through the maximum stroke of which the apparatus is capable. Initial movement overcomes the resistance of the detent spring2'5 to permit disengagement thereby of the flange 2 3a.

When it .is desired to limit the effective stroke of the (jack .to a lesser value, the pistons l9 and 20 are separated from each other, and fluid trapped between, so that the effect is to produce an elongated piston structure which obviously will have ashorter stroke in a cylinder of .given length than would the shorter piston structure that results when the two pistons l9 and 20 are in contact with each other, as shown in Fig. 1. The separation of the two pistons is achieved by rotating the arm 58 and the shaft 51 to move the actuating plug '46 to the right sufliciently to lift the ball valves 28 and 4| off their-seats, thereby establishing free communication between the opposite faces of the floating piston 20. While these valves are 'held open in the manner described, fluid is admitted slowly through the port I6 and exhausted through the port I8. This fluid flows freely through the floating piston 20 and does not exert suflicient force thereon to overcome the forceof the detent spring 25, so that the floating .piston remainsstationary, and the fluid flow moves the working .p'iston l9 away from the floating piston. When the working pistonhas beenseparated from the floating piston the desired distance, the arm 58 is released, permitting closure of the 'ball valves 28 and 4| to thereby'block escape of the fluid trapped between the two pistons and preserving the spacing therebetween until subsequent readjustment is effectedby-again actuating the arm 58.

.Fig. .2 shows the two pistons in separated positions .and in mid-stroke position within the cylinder.- i a To bring the pistons-together and thereby lengthen the stroke, the arm 158 is actuated'to "pistons limits the leftward movement 01' the working piston l9 and the piston rod [1 without affecting the limit of movement to the right.

Each time the floating piston 20 moves into its extreme left end position, as shown in Fig. 1, the detent spring .25 engages the vannular .flange 2311., which offers some resistance to movement of-the floating piston into and Eout:of extreme end position. However, this resistance is usually relatively small .as compared to the resistance offered by the mechanism controlled by the cylinder, andisof no significance. I

Although for the purpose of explaining the invention, a particular embodiment thereof has been shown and described, obvious modifications will occur to a person skilled .in the art, and I do not desire to be limited to the exact details shown and described.

I claim:

1. .-A hydraulic motor comprising: a cylinder having liquid ports at opposite ends for ingress and egress of operating liquid; a working piston within said cylinder and means connecting it to an exterior device to 'be actuated; a floating ipiston in said cylinder; means defining :a passage interconnecting the space between said two pistons with one .end of said cylinder; valve means in said passage, said valve means "being normally closed irrespective of pressures applied thereto to trap liquid between said pistons and maintain them in spaced-apart relation to thereby limit the stroke of said twopistons as .a unit in said cylinder; and means .for selectively openingsaid valve means to admit liquid to and from said space between said .pistons and thereby vary the spacing between said pistons.

2. A hydraulic motor according to claim 1 in which said valve means is located within said floating piston for intercommunicating opposite faces thereof.

3. A hydraulic motor according to claim 2 in which said valve opening means comprises longitudinally .reciprocable valve operating means in said floating piston and projecting from oneend thereof, and a cooperating actuating member Sin said cylinder adapted to be juxtaposed in operating relation to said valve actuating member when Y said floating piston is in one end position of said cylinder.

4. Apparatus according to claim 3 including means for yieldably retaining "said floating piston in said one end position in said cylinder.

CARLOS B. LIVERS.

REFERENCES CITED I The following references are of record in the file of this patent:

UNITED STATES PATENTS 

